The widely used M109 carries a 155-mm howitzer and is the ... that opens to the rear and an M27 day periscope. A .50-cal M2 heavy-barrel machine gun is pintle-mounted on the front of the cupola.

It was intended to introduce a new family of heavy vehicles for the US Army, including a successor to the M109. In 1994 ... howitzer based on the M1 Abrams tank chassis with a range of over ...